Ambulatory medical devices include implantable medical devices (IMDs) and wearable medical devices. Some examples of IMDs include cardiac function management (CFM) devices such as implantable pacemakers, implantable cardioverter defibrillators (ICDs), cardiac resynchronization therapy devices (CRTs), and devices that include a combination of such capabilities. The devices can be used to treat patients or subjects using electrical or other therapy, or to aid a physician or caregiver in patient diagnosis through internal monitoring of a patient's condition. The devices may include one or more electrodes in communication with one or more sense amplifiers to monitor electrical heart activity within a patient, and often include one or more sensors to monitor one or more other internal patient parameters. The devices may be implanted subcutaneously and may include electrodes that are able to sense cardiac signals without being in direct contact with the patient's heart. Other examples of IMDs include implantable diagnostic devices, implantable drug delivery systems, or implantable devices with neural stimulation capability (e.g., vagus nerve stimulator, baroreflex stimulator, carotid sinus stimulator, etc.).
Some examples of wearable medical devices include wearable cardioverter defibrillators (WCDs) and wearable diagnostic devices (e.g., an ambulatory monitoring vest). WCDs can be monitoring devices that include surface electrodes. The surface electrodes may be arranged to provide one or both of monitoring to provide surface electrocardiograms (ECGs) and delivery of cardioverter and defibrillator shock therapy. A wearable medical device can also include a monitoring patch worn by the patient such as an adherable patch or a patch included with an article of clothing worn by the patient.
Wireless telemetry (e.g., low power radio frequency (RF) communication) can be used to transfer information between an ambulatory medical device and a medical device communicator. However, RF communication frequencies may be limited by governing bodies or other regulatory agencies. An RF channel available for use in one communication session may not be available for another communication session, such as when the medical device and communicator are used in different countries or regulatory jurisdictions.